As technologies of light emitting diodes (LEDs) have been developed, cost reduction and energy saving are achieved. Further, apparatuses using LEDs have been diversified. Now, LEDs emitting visible light are vigorously applied to various applications including illumination, and ultraviolet (UV) light sources are widely used in science and industry, medicine, environmental science, a semiconductor industry, etc., and application areas thereof will be widened.
Light emitting diodes (an LED or LEDs) are devices which convert electrical energy into light, and an LED generally includes at least one active layer formed of a semiconductor material and interposed between a plurality of layers doped with dopants having opposite electrical characteristics. In general, when bias is applied to both ends of the doped layers, holes and electrons are injected into the active layer and are recombined in the active layer, thus generating light. Such light is emitted from the active layer through the overall surface of the LED.